1. Field of the Invention
The present invention relates to a semiconductor device, having a chip-size package structure, and a process for producing the same.
2. Description of the Related Art
A process for producing semiconductor devices comprising assembling semiconductor devices in the wafering step has been developed (Japanese Unexamined Patent Publication (Kokai) No. 10-79362). The process can provide semiconductor devices each having a separate chip-size package structure completed by cutting, and reduce the production costs.
The production process comprises forming a wiring pattern (rewiring pattern), to be connected to electrodes of the semiconductor chip, on an insulating film formed on the semiconductor chip, forming protruded electrodes by plating the wiring pattern, forming a protective film covering the wiring pattern by compression molding, and forming a solder bump for external connection on the end portion of each of the protruded electrodes.
The step of forming a protective film comprises the following procedures.
That is, a top face and a bottom face are heated to about 175xc2x0 C. A temporary film is absorbed by the top face.
A wafer on which a wiring pattern and protruded electrodes are formed is placed on the bottom face, and a sealing resin is placed on the wafer.
The resin is melted by the heat and pressure of the sealing mold to be spread over the entire wafer, and held within the mold to be cured.
The wafer is taken out of the mold, and the temporary film is peeled off.
A solder bump for external connection is formed on the end portion of each of the protruded electrodes.
However, the conventional process for producing a semiconductor device has been found to have the following problems.
That is, when the process is carried out by compression molding wherein a resin is placed on a wafer, the resin is melted by pressing the resin with a mold, and the molten resin is spread over the entire wafer to form a protective film, the protective film is also placed on the end face of each of the protruded electrodes, and removal of the protective film from the end face becomes incomplete.
Accordingly, when a solder bump 12 is bonded to the end portion of a protruded electrode 10 as shown in FIG. 16, the bond area of the solder bump 12 is reduced by a protective film 14, and the bond strength becomes insufficient, which causes a problem in reliability.
Moreover, the bonded portion of the solder bump 12 makes an acute angle with the surface of the protruded electrode 10, which causes the problem that the bump tends to be easily removed by impact.
In addition, the reference numerals 15, 16 and 18 designate a semiconductor chip, an insulating film formed from a polyimide resin and a rewiring pattern formed on the insulating film 16, respectively.
An object of the present invention is to provide a semiconductor device which is excellent in the bond strength of a bump with each of the protruded electrodes and which is highly reliable, and a process for producing the same.
In a semiconductor device according to the present invention wherein a wiring pattern to be connected to an electrode of a semiconductor chip is formed on an insulating film formed on the semiconductor chip surface on which the electrode is formed, protruded electrodes are formed on the wiring pattern, the wiring pattern is covered with a protective film, and a bump for external connection is formed on the end portion of each of the protruded electrodes. exposed from the protective film, the bump is formed by bonding the bump to the at least entire end face of each of the protruded electrodes.
Since the bump is bonded to the entire end face of each of the protruded electrodes as described above, the bump is excellent in bond strength.
The bump mentioned above is characterized in that a barrier plated layer is formed on the end face of each of the protruded electrodes, and that the bump is formed in such a manner that the bump is bonded to the entire barrier plated layer.
Since the bump shows good wettability with the barrier plated layer, it is bonded to the entire barrier plated layer.
The protective film is characterized in that the protective film is formed to have a top surface lower than the position at which the bump is bonded to each of the protruded electrodes.
Since the top surface of the protective film is lower than that of the protruded electrodes, the protective film is never placed on the end portion of the protruded electrodes, and the bump is bonded to the entire end face of each of the protruded electrodes.
The protruded electrodes are appropriate when an oxide film is formed on the peripheral surface of each of the protruded electrodes, and when there is a gap between the protective film and the peripheral surface of each of the protruded electrodes.
The protruded electrodes thus become independent of the protective film, and are not influenced thereby even when the coefficient of thermal expansion of the electrodes differs from that of the film. Stress concentration between the protruded electrode and the bump is therefore relaxed, and crack formation and the like, in the bump and in the protective film, can be suppressed.
Furthermore, it is also appropriate in this case to form the protective film in such a manner that the level of the protective film becomes higher than the position at which the bump is bonded to each of the protruded electrodes, and that part of the peripheral surface of the bump is contacted with the protective film.
As a result, a gap between each of the electrodes and the protective film can be closed, and invasion of moisture, etc. can be prevented.
Next, in a process for producing a semiconductor device according to the present invention wherein a wiring pattern to be connected to an electrode of a semiconductor chip is formed on an insulating film formed on the semiconductor chip surface on which the electrode is formed, protruded electrodes are formed on the wiring pattern, the wiring pattern is covered with a protective film, and a bump for external connection is formed on the end portion of each of the protruded electrodes exposed from the protective film, the process comprises the steps of: covering the wiring pattern formed on the insulating film with a resist layer, and forming holes in the resist layer to expose part of the wiring pattern; plating the wiring pattern within the holes to form the protruded electrodes; removing the resist layer; effecting sealing by supplying a resin to the wiring pattern to form a resin layer having a top surface lower than that of the protruded electrodes, thereby forming a protective film; and forming a bump on each of the protruded electrodes in such a manner that the bump is bonded to the at least entire end face of each of the protruded electrodes.
Since the protective film is formed by potting or spin coating to have a top surface lower than that of each of the protruded electrodes, the entire end face of each of the protruded electrodes is exposed, and a bump is bonded to the entire end face, which improves the bond strength of the bump.
Moreover, the process is appropriate when the process comprises plating to form a barrier plated layer on the end face of each of the protruded electrodes, and when the bump is formed in the bump-forming step in such a manner that the bump is bonded to the entire barrier plated layer.
Furthermore, in a process for producing a semiconductor device according to the present invention wherein a wiring pattern to be connected to an electrode of a semiconductor chip is formed on an insulating film formed on the semiconductor chip surface on which the electrode is formed, protruded electrodes are formed on the wiring pattern, the wiring pattern is covered with a protective film, and a bump for external connection is formed on the end portion of each of the protruded electrodes exposed from the protective film, the process comprises the steps of: covering the wiring pattern formed on the insulating film with a resist layer, and forming holes in the resist layer to expose part of the wiring pattern; plating the wiring pattern within the holes to form the protruded electrodes; removing the resist layer; forming the bump on each of the protruded electrodes in such a manner that the bump is bonded to the at least entire end face of each of the protruded electrodes; and effecting sealing, after forming the bump, by supplying a resin to the wiring pattern to form a protective film.
Since the protective film is formed after forming bumps, the bumps each can be formed at a desired position of the protruded electrode, and the bond strength of the bumps can be increased.
Also in this case, the process is appropriate when the process comprises the plating step of forming a barrier plated layer on the end face of each of the protruded electrodes, and when the bump is formed in the bump-forming step in such a manner that the bump is bonded to the entire barrier plated layer.
Furthermore, in a process for producing a semiconductor device according to the present invention wherein a wiring pattern to be connected to an electrode of a semiconductor chip is formed on an insulating film formed on the semiconductor chip surface on which the electrode is formed, protruded electrodes are formed on the wiring pattern, the wiring pattern is covered with a protective film, and a bump for external connection is formed on the end portion of each of the protruded electrodes exposed from the protective film, the process comprises the steps of: covering the wiring pattern formed on the insulating film with a resist layer, and forming holes in the resist layer to expose part of the wiring pattern; plating the wiring pattern within the holes to form the protruded electrodes; removing the resist layer; forming the bump on each of the protruded electrodes in such a manner that the bump is bonded to the at least entire end face of each of the protruded electrodes; forming a photosensitive resist layer to cover the wiring pattern and the protruded electrodes; and effecting photolithography by exposing to light and developing the photosensitive resist layer to form a protective film which covers the wiring pattern and to expose the protruded electrodes.
Since the protective film is formed after forming bumps also in this process, the bumps can be formed without being influenced by the protective film, and the bond strength of the bumps can be increased.